Re: How to troubleshoot a faulty 7B92A?

Thierry Delaitre

Thanks. Here are some observations from the measurements around the U820 sweep control IC on the horizontal logic board 7

U820 - Sweep control IC
- Pin 6 (auto delay) is 0.5V ; strange ?? other side of the R828 resistor (180K) is 14.7V
- Pin 7 (trig D) is 0.5V
- Pin 8 (hold off timing) is 0V ; strange? according to the schematic there is a pull-up resistor to the 15V line
- Pin 10 (hold off) shows a 4V DC voltage (no sweep)
- Pin 17 (trig disable) is 0V
- Pin 18 (lockout) is low
- Pin 19 (auto mode) is low as it should for auto triggered



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